Semiconductor transistors, in particular field-effect controlled switching devices such as a Metal Oxide Semiconductor Field Effect Transistor (MOSFET) or an Insulated Gate Bipolar Transistor (IGBT), have been used for various applications including but not limited to use as switches in power supplies and power converters, electric cars, air-conditioners, and even stereo systems. Particularly with regard to power devices capable of switching large currents and/or operating at higher voltages, a low on-state resistance Ron and high breakdown voltages Ubd are often desired.
To achieve low on-state resistance Ron and high breakdown voltages Ubd, charge-compensation semiconductor devices were developed. The compensation principle is based on a mutual compensation of charges in n- and p-doped regions, which may be implemented as n- and p-doped pillar regions or wall-shaped regions, in the drift zone of a vertical MOSFET.
Typically, the charge-compensation structure formed by p-type and n-type regions is arranged below the actual MOSFET-structure, with its source, body regions and gate regions, and also below the associated MOS-channels that are arranged next to one another in the semiconductor volume of the semiconductor device or interleaved with one another in such a way that, in the off-state, their charges can be mutually depleted and that, in the activated state or on-state, there results an uninterrupted, low-impedance conduction path from a source electrode near the surface to a drain electrode arranged on the back side.
By virtue of the compensation of the p-type and n-type dopings, the doping of the current-carrying region can be significantly increased in the case of compensation components, which results in a significant reduction of the on-state resistance Ron despite the loss of a (current-carrying) active area A. The reduction of the on-state resistance Ron times the active chip area A, in the following also referred to as (area) specific on-state resistance Ron*A, of such semiconductor power devices is associated with a reduction of the heat generated by the current in the on-state, so that such semiconductor power devices with charge-compensation structure remain “cool” compared with conventional semiconductor power devices.
However, the specific on-state resistance Ron*A of charge-compensation semiconductor devices may only decrease with lowering pitch of the compensation regions up to a limit and even increase when the pitch is further lowered.
Accordingly, there is a need to improve charge-compensation semiconductor devices and manufacturing of those semiconductor devices.